What does a piece of ice without dust mean?

The famous phrase "A Ice Heart" comes from Wang Changling's Farewell to Xin Jian in Furong Inn in the Tang Dynasty: "Cold rain enters the lake day and night, and it is plain and clean to send guests to the lonely mountain. If relatives and friends in Luoyang ask each other, a piece of ice heart is in the jade pot ",which mainly means that after a night of cold rain, the poet said goodbye to his friends in the Furong Building, and only the morning light reflected the distant mountains. He told his friends that if relatives and friends in Luoyang ask about me, please convey my honest and clean mind to them. This is a poem to bid farewell to a friend. At the same time, the author uses a crystal clear Bing Xin jade pot to describe his frankness and indifference. "Dust-free" and "a piece of ice heart" are the same meaning.